1. Field of the Invention
The invention relates to a gain control method for a radio receiver having to pick up signals corresponding to packets of digital data which are transmitted in bursts.
It also relates to a receiver arranged to allow the exploitation of this method.
2. Description of Related Art
In the field of wireless transmissions and because of the possibilities of relative positioning between transmitter and receiver, a very broad received dynamic power range may have to be exploited. This is especially the case when a transmitter is exploited in connection with mobile receivers and when the power of this transmitter is adjusted in order to allow a distant receiver to receive with enough power when it is under barely favourable conditions, for example at the limit of the region of coverage, which may lead to the reception taking place at high power for a receiver located close to the transmitter.
The proper operation of a receiver with a broad power level range on reception may be difficult to obtain, in particular in the case of a receiver receiving signals corresponding to packets of data transmitted in bursts. It is therefore necessary that the receiver be capable of detecting, without faults, the arrival of a burst preamble which characterizes the arrival of packets. It is therefore necessary that it be capable of quickly adjusting its gain, in order to be able to take account of the packets which follow the preamble of a burst and which constitute the useful part of this burst, whatever the power of the signals received within a particular receiving range.
Receivers are known which have an automatic gain controller acting on the level of the analogue signals which are obtained from signals received by radio and which are then converted into digital form for exploitation.
According to a known embodiment, the received signal level is measured during the preamble contained in signals corresponding to a packet burst and the correction is carried out while the rest of the burst is received. There is therefore a risk that the signals subjected to analogue/digital conversion are degraded and that the result of the conversion is incorrect.